Sidewall image transfer (SIT) processes are often used during integrated circuit (IC) fabrication to pattern relatively narrow, essentially parallel, rectangular shaped features (e.g., semiconductor fins for fin-type field effect transistors (FINFETs), gate structures for various types of field effect transistors (FETs), metal wires, trenches for metal wires, etc.). SIT processing typically involves the formation of a mandrel layer on a target layer (i.e., on a layer to be patterned), the formation of mandrels (e.g., rectangular shaped bodies) from the mandrel layer using lithographic patterning and etch processes, the formation of sidewall spacers on the mandrels, the selective removal of the mandrels and the cutting of one or more of the sidewall spacers at one or more locations using lithographic patterning and etch processes to form spacer segments of desired lengths. Once the sidewall spacers are cut, thereby completing the formation of a sidewall spacer pattern (i.e., a pattern of sidewall spacers), an etch process can be performed to transfer the image of the sidewall spacer pattern (i.e., the image of the sidewall spacers or remaining segments thereof) into the target layer below.
However, as the size of technology nodes continues to decrease and, more particularly, as the spacer pitch in sidewall spacer patterns continues to decrease so that the density of patterned features within the target layer increases, overlay errors associated with spacer cuts (i.e., associated with the lithographic patterning and etching of spacer cut openings) have more of an impact. Specifically, during the lithographic and etch processes used to form openings that cut through sidewall spacers, overlay errors can occur. When the spacer pitch and the spacer cut length are relatively close in size, an overlay error with respect to a spacer cut opening over a sidewall spacer to be cut can result in, not only an incomplete cut of the sidewall spacer, but also an unwanted cut of an adjacent sidewall spacer. Incomplete sidewall spacer cuts and/or unwanted sidewall spacer cuts can, in turn, result in pattern errors in the pattern that is transferred into the target layer. One technique for avoiding the above-described sidewall spacer cut process involves cutting the mandrel(s) before sidewall spacer formation (referred to as a mandrel cut first technique). However, this mandrel cut first technique is inefficient in terms of time and resources. Therefore, there is a need in the art for an improved method of forming a sidewall spacer pattern.